Technical Field
The present application relates to a method for controlling a bit rate and an apparatus therefor, and more specifically to an apparatus, which stores a bit rate varied according to a significance level in a memory, and a method for determining a bit rate.
Description of the Related Art
As a social interest in a security increases, demands on a black box monitoring camera or a security camera becomes higher.
A main function of a device for obtaining image information on a predetermined area detects an event such as appearance or a suspected object in a camera area and compresses and stores data according to image information which is obtained until the event is terminated.
Because the device for obtaining image information receives power from a battery (e.g., a security camera operated by a battery of a vehicle when the vehicle is parked during a few weeks), a reduction in energy consumption is one of the most important issues.
FIG. 1 is a block diagram illustrating a conventional device satisfying such a main function. Referring to FIG. 1, a conventional device 100 may operate in an event-driven manner to protect energy consumption according to storage of a frame including less important information.
That is, other function blocks except for an event detector 120 are generally power-gated and wake up and operate whenever the event detector 120 detects an event.
A significance level of image information obtained when an event lasts is variable. For example, a significance level of image information including a face image is higher than that of image information including the back of his/her head.
The significance level is measured through various algorithms such as background subtraction, face detection and recognition, object tracking, behavior analysis, and the like.
A result of the measured significance level is used to adjust video encoding of a video encoder 140 (e.g., a manner of encoding image information having a high significance level using high image quality).
Generally, an encoding configuration with a high bit rate and low compression efficiency of an encoding frame needs power consumption units of which the number is smaller than that with high compression efficiency.
However, as a bit rate of an encoder increases, the energy consumption needed to store encoded image information in a memory increases.
That is, there is an energy trade-off on a video encoding configuration.
Furthermore, a memory embedded in an imaging device has a limited memory space to reduce the cost of the imaging device overall.
Accordingly, determination of a bit rate for encoding has to satisfy a restriction on a memory space in order to consider such constraints.
The encoding bit rate for minimizing energy depends on an event behavior specified by frequency of event occurrence and duration.
However, because the event behavior is nondeterministic and non-static, a time-driven encoding bit rate configuration according to the predetermined event behavior is inaccurate and inefficient.